The abundant natural bentonite from Sarolangun deposit of Jambi Province, Indonesia, has been successfully activated by a wet acid activation method and applied as a low-cost, and environmental-friendly adsorbent for Congo red dye removal from aqueous solution. The activated bentonite samples were characterized by powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N₂ adsorption-desorption, and X-ray fluorescence (XRF). The batch adsorption technique has been conducted to study the adsorption behavior of Congo red on activated bentonite. The effects of operational parameters toward the Congo red adsorption on activated bentonite, including adsorbent dosage, initial pH, contact time, initial concentration, and temperature were investigated. Moreover, the properties of adsorption kinetics, adsorption isotherm, and adsorption thermodynamic were also investigated. The results of material characterization showed that acid-activated bentonite has better properties than natural bentonite. For instance, the surface area of acid-activated bentonite elevated almost five-fold compared with natural bentonite. The batch adsorption study showed that the Congo red adsorption on acid-activated bentonite was significantly affected by adsorbent dosage, initial pH, contact time, dye concentration, and temperature. The adsorption kinetics investigation revealed that adsorption was best evaluated by a pseudo-second-order model rather than pseudo-first-order model. The adsorption equilibrium study described that the adsorption process followed the Langmuir isotherm model. The result of thermodynamic investigation revealed that the adsorption process occurred spontaneously and favorably in high-temperature conditions.

The effects of the polytetrafluoroethylene (PTFE) content and sintering temperature on the properties of a fuel cell electrode backing layer are studied in this work. Characterization of the electrical conductivity, hydrophobicity, and surface structure of the backing layer is carried out for various PTFE content values (15–45 wt. %) and sintering temperatures (175–400 °C). The results showed that, generally, the electrical conductivity of the backing layer surface decreased whereas the hydrophobicity increased as the PTFE content and the sintering temperature increased. Based on the observations made via scanning electron microscope (SEM) analysis and testing of the electrical conductivity and hydrophobicity, the PTFE content should not exceed 35 wt. %, and the best sintering temperature was 350 °C.

Adsorption of congo red on bentonite was studied kinetics and thermodynamically. Bentonite was physically activated at various temperatures and characterized using X-ray, and infrared. By increasing thermal temperature activation up to 500 °C can decrease the montmorillonite fraction with decreasing the peak was observed. The kinetic of adsorption suggests that the interaction of congo red-bentonite could be best represented by the first-order kinetics of Langmuir-Hinshelwood model. The adsorption process was exothermic with ΔH in the range -4.43 to -9.76 kJ.mol⁻¹ accompanied by increase in Gibbs energy. All results have shown that bentonite after physical activation could be used as an adsorbent for congo red adsorption.